Thousands of Iraqi Kurdish forces, supported by U.S. and other fighter jets, attacked a key highway in northern Iraq, part of a new offensive to recapture the strategic town of Sinjar from Islamic State (IS) militants.

Fighters from the Kurdish Peshmerga militia launched their offensive just after dawn on November 12, advancing on Highway 47 toward Sinjar from three directions.

Video showed long lines of pickup trucks escorted by fighters on foot as they began the attack. Loud explosions could be heard in the distance.

By midday, the Kurdish Regional Security Council said its forces controlled a section of Highway 47.

U.S. Defense Department spokesman Peter Cook said U.S. military personnel were on the ground, behind the front lines, helping to guide air strikes. Aircraft from the U.S.-led coalition battling Islamic State hit 36 targets overnight, he said.

Sinjar sits along a key supply line for militants between Islamic State-held territory in Syria and Mosul, Iraq’s second-largest city and a stronghold for the radical group.

IS fighters overran the town in August 2014, forcing tens of thousands of people from the Yazidi minority to flee into the mountains nearby.

“Iraqi Kurdish forces are in the lead of this offensive with U.S. personnel in support,” Cook said. The highway is a “key conduit [and] if it is severed, it does potentially mean a significant impact on [IS] operations in Iraq.”

"We expect that the [Islamic State] forces will be dug in, will have placed defensive measures, put those in place to try and hold this ground," he said. "So we do not expect this is going to be an easy fight, but we do have confidence in these, in the Iraqi Kurdish forces there who have shown their capability in the past."

After seizing Sinjar last year, Islamic State fighters massacred thousands of Yazidis and enslaved an unknown number of women, prompting the United States to begin air strikes and form an international coalition to battle the extremist group not only in Iraq but also in Syria.

News reports said Yazidi fighters were also among the units involved in the offensive that started November 12.

Sinjar is located at the foot of Mount Sinjar about 50 kilometers from the Syrian border. An attempt by the Kurds to retake it stalled in December. The militants have been reinforcing their ranks in Sinjar recently in expectation of an assault, although the coalition did not give specifics on the size of the IS forces.